Art of removing wax from oil



-Patented- May 1, Q

UNITED STATES PATENT oFF1cE.-'

GEORGE D. GRAVES, OF CASPER, WYOMING, ASSIGNOB T0 STANDARD OIL COMPANY,

' OF WRITING, INDIANA, A CORPORATION OF INDIANA.

'AB'I. OI REMOVING" WAX. FROM OIL.

No Drawing. Application filed July 27,

The'present invention relates to improvements in the removal of wax from 011, and more particularly from wax-containing viscons fractions derived by distillation under non-cracking conditions, particularly with fire and steam or under vacuum. It will be ,fully understood from the following description, in which an embodiment of the invention is set forth.

In the distillation of petroleum oils-with fire and steam and under vacuum, and to a lesser extent in the distillation, when conducted under non-cracking conditions, the wax distillate is found to contain wax of such a nature as to be difiicult of separation by filter pressing, and the resulting wax can be sweated only with difiiculty, if at' all. The most common method of handling such distillates in oil refineries is' b .re-running, in which operation some cecomposition takes place. The distillate from this re-run ning operation found to be easily pressed and the resulting wax easily. sweated. The decomposition occurring during the lie-running operation, however, results in a large loss of viscous lubricant fractions, and the expense of the re-running operation is itself considerable. Other methods of handling such distillates have been proposed, such as diluting, chilling and centrifuging; diluting with wax-free oil and pressing; diluting with oils containing readily filtrable wax and the like. i v In aecordancewith the present invention, wax is removed from wax distillate of the character above set forth in. the following manner 1 The wax'distillate is brought cooling 1 or otherwise to a temperature of 0 to '90 F., (at least below its cloud point slightly above its cold test). At such temperatures certain wax constituents of the oil are found to crystallize out, and the oil is put through filter presses. in the ordinary manner,- and a cake of wax is found to bulld up, the wax being of a fairly dry, 'crumblycharacter." The proportion of wax thus removed of course varies with the of oil employed; om

in the case of a wax distillate derived a Wyoming crudeoil it was found to-be in the neighborhood of 2% on'the oil pressed, the oil being'a distillate of an average gravity of 30.5 A. P. I. derived from continu-.. ous fire and steam distillation. The wa;x thus obtained is of the character of slo'p.

int a tem remains in solution in the oil, and below the 1925. Serial No. 46,490.

wax. Somewhat lower or higher tempera? tures maybe employed; at higher temperatures some of the S101) wax tends to remain in the oiland atlower temperatures a more perfect separation of the slop wax may be secured.

The pressed distillate contains the ordinary parafiin wax present in the oil, and may, according to the temperature employed in the first pressing operation, contain small.

amountsof slop wax insuflicient to interfere with the pressing and sweating of the paraflin wax. The pressed distillate from the first pressing operation is then chilled and pressed as in ordinary methods of separatingparaflin wax from wax distillate; thus, for certain types of oils, it may be chilled to 20 F. and filter-pressed in the usual manner. 1f lower cold test lubricants are desired from the wax distillate, the temperature to which it is chilled may be lower,

or a second pressing operation may be carried out at lower temperature,'asin ordi-' nary practice.

The slop wax derived from the first pressing operation is of somewhat higher melting point than ordinary paraflin wax, its melting point being, on an average, from 138 to 140 F. Onfractional crystallization, it is found to yield separable products having a melting point range from 125 to 158 F. In

accordance with this invention, it is removed from the wax distillate at a temperature at which substantially allot the paraffin wax remains in solution. It may not be admixed with paraflin wax prior tosweating, as it seriously interferes with the sweating of oil from paraflin-wax when present in amounts appreciably greater than'from 2 to 3% of the i A though the present invention has been described in connection with a s method of carrying it into effect, it Is not intended that the details hereinbefore set forth shall beregarded as limitations upon the scope of the claimsexeept in so far as included in the accompanyingclaims. IClfl-lllli' i I I 1 The method of removing waxes which hinder filtration orv sweating of ordinary paraflin wax from oil distillates con principally paraflin'wax together with w. I

waxes, comprising filtersueh ml rature at which the .wax

temperature at which the first mentioned waxes are crystallized from the oil, thereby producing as a filtrate a filter-pressible parafiin wax-containin oil.

2. The method 0 removing slop .wax from distillate oils containing principally parafiin wax together with slop wax, comprising filter-pressing such oils at temperatures of V .70 to 90 F., thereby roducing as a filtrate a filter-pressable para n wax-containing oil.

3. The method of removing wax from distillate oils containing principally parafiin wax together with slop wax oomprismg filter-pressing the oil/at a temperature below I its cloud point and ahove the temperature at l 

